WHITE ON NEW INVERTEBRATES. 719 



garded as a fresh-water shell, and is often found associated with other 

 fresh-water forms, and also with Nuculana, which is now known only in 

 marine waters. Its other associates are Corbula, GorMcula, and Anomia. 

 Position and locality. — Laramie Group, about 400 feet above its base, 

 Danforth Hills, Northwestern Colorado. The locality is about 10 miles 

 northeastward from White Eiver Indian agency. 



